Dr Kwang Meng Cham
BOptom PGCertOcTher GCertUniTeach PhD
BOptom BSc(Hons) PGCertOcTher GCertUniTeach
Department of Optometry and Vision Sciences, The University of Melbourne
The term ‘white without pressure’ (WWOP) refers to focal or circumferential semi-translucent greyish-white retinal areas with smooth or scalloped margins and a deep red posterior border, most often located between the equator and ora serrata.1,2
They resemble the appearance of ‘white with pressure’ (WWP) but are visible without external pressure applied to the eye with scleral indentation. There has been some suggestion that WWOP may represent an advanced form of WWP.2
WWOP is most frequently bilateral2 and found in the temporal retina,2,3 but it can be more extensive and involve the entire retinal periphery,3 occur as far posteriorly as the peri-macular region,1 contain islands of normal tissue making distinction from retinal holes difficult,1 and change location over time.4 Cases of dark-without-pressure fundus lesions have also been reported, albeit limitedly, and present in similar locations.5
The reported prevalence of WWOP varies greatly in the literature, from as low as three per cent for the general population to up to 75 per cent for high myopes.2,6,7 Generally the prevalence increases with axial length2,6 and high myopia.2,6 Frequency of WWOP declines with age2,6,8 and it does not show a consistent predilection for gender.1,7
Some variation with ethnicity has been reported, with the lowest prevalence reported for Caucasian populations and higher prevalence reported for individuals with darker-pigmented skin.1,2 Higher prevalence reported for individuals of Asian background7 are confounded by higher degrees of refractive error and axial length. Prevalence variation can also be attributed in part to differences in fundus pigmentation5 and retinal examination techniques.
Although the pathological basis of WWOP remains uncertain, the retinal appearance is speculated to arise from mild vitreal traction and/or vitreo-retinal adhesions.2,3,6 Spectral domain optical coherence tomography (SD-OCT) has demonstrated hyper-reflectance of the outer retina in eyes with WWOP.5,9
These structural changes may result from ocular enlargement and/or vitreous base tractional forces.8 Structural change to the photoreceptors has been postulated for both WWOP and dark without pressure,5 but functional changes are yet to be identified. Altered peripheral vascular perfusion has also been demonstrated in eyes with WWOP by fluorescein angiography but it is unknown if this finding is causal.10
The association between WWOP and retinal tears and rhegmatogenous retinal detachment (RRD) is not clearly demonstrated in the literature. However, the risk of RRD must be considered given the association between WWOP and axial length2,6 and peripheral degenerations such as lattice,1,2 the proposed role of vitreous traction in the development of WWOP9 and the reported link between WWP and giant tears.11 Here we report the clinical observations for five optometry students in whom WWOP was detected during ocular fundus examination training sessions using a variety of examination techniques.
All individuals in whom WWOP was identified underwent a standard clinical history, basic screening, subjective refraction with vertex distance measurement to facilitate conversion to the ocular plane, corneal topography, and slitlamp, 90 D fundus lens biomicroscopy and BIO examination through dilated pupils.
The posterior pole, peripheral retina and vitreous were examined in all nine cardinal positions of gaze using both BIO and a 90 D fundus lens. The maculae and optic nerve heads were further screened by OCT (3D macula and disc scans, Topcon 3D OCT-2000, Tokyo, Japan).
Anterior vitreous detachment (AVD) and posterior vitreous detachment (PVD) were detected by inspecting the anterior and posterior vitreous by slitlamp alone (AVD and PVD) and 90 D fundus lens biomicroscopy to identify the Weiss ring (PVD). Areas displaying WWOP were documented and imaged by the Optos Optomap (Optos, Dunfermline, Scotland, UK).
WWOP was identified incidentally in five optometry students by their peers, in a class of 59 students (eight per cent). All individuals were of Asian background and 22 years of age (three males and two females).
Table 1. Clinical characteristics of five individuals with WWOP
Table 1 summarises the clinical characteristics of each individual that relate to their refractive error status and WWOP. All individuals reported longstanding floaters in one (case 3) or both eyes (cases 1, 2, 4 and 5). Only two individuals (cases 2 and 4) reported a previous episode of photopsia that was brief in duration and suggestive of vitreo-retinal traction.12
No individuals reported any other significant personal ocular history including operations, infections and trauma. There was no family history of blindness, retinal detachment, tears or holes. A family history of high myopia was reported by three individuals (cases 2, 4 and 5). Mean refractive error (RE) at the ocular plane of affected eyes was -4.8 ± 2.0 D (mean ± SD) and ranged from emmetropia (-0.4 D, case 3) to high myopia (-6.7 D, case 2), with four myopic individuals who have worn a spectacle correction from 13 years of age or earlier. The only emmetrope (case 3) displayed a flat cornea curvature (CC). Best-corrected visual acuities (BCVA) were 6/7.5++ or better and confrontation was full to finger counting for all individuals. OCT revealed the optic nerve head and macula to be normal in all individuals.
WWOP presented as areas of pale, flat retina with distinct curvilinear or scalloped margins, located between the equator and ora serrata. The demarcating retina often appeared redder than the surrounding normal retina and displayed a band of increased vitreo-retinal reflectance. WWOP occurred bilaterally in three individuals (cases 1, 2 and 5), unilaterally in two (cases 3 and 4), in all sectors for three (cases 1, 2 and 3), and was limited to the temporal retina for two (cases 4 and 5).
Overall, WWOP was identified in more than one location in five of eight (63 per cent) affected eyes. PVD was noted in two individuals (cases 1 and 2). There was no evidence of additional peripheral retinal pathology, including lattice degeneration, retinal tears and holes. The clinical appearances of WWOP of three representative cases are shown in Figures 1, 2 and 3.
Figure 1. Optos Optomap image of case 1 (right eye). WWOP extended to all sectors of the retina bilaterally. Affected retinal areas appeared pale and flat and the margins were scalloped and redder than the surrounding retina (large arrows).
Figure 2. Optos Optomap image of case 2 (right eye). WWOP extended to all sectors of the retina bilaterally. Affected retinal areas appeared pale and flat. Margins were curvilinear or scalloped, redder than surrounding retina (large arrows) and displayed greater vitreo-retinal reflectance in parts (small arrows).
Figure 3. Optos Optomap image of case 3 (left eye). WWOP was unilateral, variable in configuration and extended to all sectors. Affected retinal areas appeared paler than the surrounding retina and flat. Margins were largely curvilinear and in parts sharp-edged, redder than surrounding retina (large arrows) and/or displayed greater vitreo-retinal reflectance (small arrows).
WWOP is a relatively common finding in young patients and while this study was not designed to determine the prevalence of WWOP in a student population, our observations have supported the published literature.2,6
WWOP occurs more frequently in high myopes but it can be identified in emmetropes and moderate myopes2,6 (Table 1), presumably as a result of excessive axial elongation. Although axial length was not measured in this study, most affected eyes were myopic (-4.8 ± 2.0 D, Table 1), the flatter cornea noted for the emmetropic case (CC 8.4 mm cf reported mean for emmetropes of 7.8 ± 0.3 mm13) suggested that axial length or vitreous chamber elongation may also be implicated in the pathogenesis of WWOP in this individual.
WWOP may vary in appearance, with broad or sharp, curvilinear or scalloped, and dark red or relatively indistinct borders, with or without increased vitreo-retinal reflectance (Figures 1, 2 and 3).1,2 Its location also varies between individuals but it often occurs bilaterally, in the peripheral retina (particularly temporally)2,3 and in more than one retinal location (Table 1).
This diversity may reflect variations in the dynamic relationship between the vitreous and the retina.2,3 Although there was no overt clinical evidence for the role of vitreo-retinal traction in the pathogenesis of WWOP in this study, all individuals reported seeing floaters.
Floaters are commonly reported by patients, particularly by individuals with vitreo-retinal pathology14 including RRD,15 but that reported here is higher than that reported for the general community.16 Variation in the extent of adhesion of the anterior/posterior vitreous face to the lens/retina suggests variable vitreo-retinal forces may be operational in these individuals in the periphery.
Clinicians should familiarise themselves with the diverse clinical presentation of WWOP to assist with distinguishing it from more serious retinal pathologies. Important differentials of WWOP include RRD and non-RRD (for example, exudative) detachment, choroidal detachment (kissing choroidals), retinal holes and tears, retinoschisis, and commotio retinae.
While multiple forms of peripheral retinal pathology can coexist in myopic eyes,7 WWOP was found in isolation in this sample. Dilated stereoscopic fundus examination is required for the identification and accurate and comprehensive documentation of peripheral lesions, and to establish that the retina is flat, non-oedematous, and devoid of tears, holes and significant vitreo-retinal traction.
To achieve an optimal view when examining the peripheral retina, a combination of 2.5% phenylephrine and 1.0% tropicamide can be used to achieve maximal dilation with scleral indentation. Peripheral fundus imaging can further assist with its identification and documentation, but care must be taken when interpreting the images, due to the variable presentation of WWOP, and although it can well supplement a dilated fundus examination, it should not replace it.
Although OCT was not performed over areas of WWOP in this study, this technology can be used to help discern if the retina is flat and to detect changes to the outer retina.5,8 Once WWOP has been diagnosed, annual review is consistent with many clinical protocols. Patients should also be warned of the symptoms suggestive of acute retinal detachment.
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